Configuring the buffered read size

Configuring the buffered read size can reduce problems with wasted disk I/) and unnecessary garbage collection.

On read workloads, Cassandra 2.1 reads drastically more data than it emits over the network. This causes problems throughput the system by wasting disk I/O and causing unnecessary garbage collection (GC).

The location of the file depends on the type of installation:
Package installations /etc/cassandra/
Tarball installations install_location/conf/


  1. Open the file for editing and scroll down to the JVM_OPTS.
  2. Set a value for the buffered read size. By default, the size is 65536.
    JVM_OPTS="$JVM_OPTS -Dcassandra.rar_buffer_size=65536"